There are conflicting opinions about donating blood while breastfeeding. The US Red Cross okays blood donation for nursing moms after 6 weeks postpartum. Donating blood causes a small loss of blood volume (and therefore a loss of fluid), so there is a theoretical possibility for a short-term temporary reduction in milk supply. Moms with vulnerable supplies may want to avoid donation. In general, women who are not pregnant, have good iron levels (that will be tested before donation), are not taking antibiotics, and are at least 100 pounds are good candidates for blood donation.
Assuming you're not at risk for anemia or other medical problems that would prohibit you from donating, the American Red Cross will allow you to donate blood if it's been at least six weeks since you delivered your baby. You do lose hydration when you donate, and since your milk supply is dependent on your being well hydrated, you should drink water before and after donating blood. Having a 200- to 300-calorie snack before or after can also help you feel better after you donate.
According to Health Sciences Authority, you should not donate blood if you are still breastfeeding because it may deplete the iron stores in your body and affect your baby's iron intake from your breast milk. As much as it is charitable to donate blood, your baby comes first. http://donorcare.hsa.gov.sg/internet/dcController?next=i_donorcare_question
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